Series parallel wiring confirmation

[rlsound]

Hey guys,

Another bone head question, just verifying that these subwoofers are wired for series/parallel correctly;


Four subwoofers, single 8ohm drivers in each. 2 subwoofer boxes are wired in series, and the other 2 are parallelled to the terminals ( neg to neg, pos to pos ) to the boxes that are wired in series.

Is this correct?

[JBL 4645]

A simple read of wiring Series or Parallel.
http://www.termpro.com/articles/spkrz.html

I think there are some JBL professional models that need the wiring reversed if I recall reading back a few years. Which models I have no idea now, best check with the JBL pro site, http://www.jblpro.com/ as they have listing in the archives vintage and new. Unless someone here knows of the top of there head which models have the wiring reversed.


Parallel is just + to – from amp to speakers
Series is like daisy chain the wires + from amp to speaker from – output on first speaker to the next speakers + input and from – on the last speaker straight back to the amps – output.

Trade off with series is you need a lot of power otherwise you’d be under powering the speakers, placing strain on the amp.

Parallel increases level with less power but I think you have to watch out for the impedance for the amp otherwise you might end up in bit of pickle.

Two 4ohm wired in parallel sums up to around 8ohms
Two 4ohm wired in series I think that lowers the impendence value down to around near 2ohms
Two 8ohms wired in parallel sums up to 16ohms, (please someone correct me, if I’m in error, mathematics is not my strongest point).

[rlsound]

As I understand it, all the JBL models that were a direct replacement for models that were reverse wiring kept that scheme.

Ie. 2245, replacement is the 2241, they are wired the same, where 2242 is wired the regular way.

[JBL 4645]

Only way to test it! Is to place a little 1.5volt battery on the terminals and watch for forward or backward cone moment! ;) It won’t self-destruct the amp wiring the terminals around the wrong way, it only inverts the sound.

Those models sound about right. I think its mentioned on the specification paper for my JBL 2240, about international wiring.

If one should go faulty in series the whole stack will go out! If wired in Parallel and one should go out the rest will remain ON. Just like looking for the faulty light on those 100 light Christmas lights that are wired in series, that was working soundly a year before.:D

When I wired up my surrounds a few years ago in series I noticed a hard popping sound on loud peak sounds, not good idea to wire them up in this fashion for the amp. I then changed it around to parallel and the issue was sorted.

So if you hear a loud popping sound coming from the subs it’s not a good sign.

[rlsound]

funny you mention a popping sound, that's exactly what's happening.

I'd like to keep an 8 ohm load on the amp, since there is only one wire running down into the auditorium.

Amp is bridged QSC EX4000, running 4 EV 3512 boxes. I'd like to do home runs back to the booth but I don't think that's going to happen.

[Allanvh5150]

To answer your first question, yes, you are correct. Out of curiosity, what size amp are you driving these with? The popping sound could be the amp clipping or the voice coils bottoming out due to overexcursion.

Allan.

[JBL 4645]

To answer your first question, yes, you are correct. Out of curiosity, what size amp are you driving these with? The popping sound could be the amp clipping or the voice coils bottoming out due to overexcursion.

Allan.

I agree with Al

Also it’s like a (popping crackling noise) that is audible over the low tones and that’s why it sounds noticeable!

Yeah Al if the amp has an clipping LED shouldn’t the LED indicate on the amp? Or would it only indicate if the amp is being driven at full level! I don’t think the LED would come ON. Maybe it’s just the wiring that the amp doesn’t like to see!

Also there’s another unforeseen issue that might be the cause. Listening position where the sub might be or might not be EQ and listener feels there is lack of low end in a few parts of the frequency response, thus forcing him/her to play it harder and near to running out of headroom on the amp! That would cause a lot clipping issues!

Or excessive EQ has been added that’s limiting the headroom and clipping can happen at EQ end sending the noise into the amp.

[Ruediger]

A low frequency speaker "sees" a generator impedance of hopefully much less than an Ohm. It consists of:
a) the amplifier's output impedance, e.g. 0.04 Ohm
b) cable resistance, e.g. 0.1 Ohm
c) resistance of series coil in the crossover, e.g. 0.5 Ohm
When using an active crossover You can get rid of "c", and it pays to invest in "b" (thicker cables).
This combined generator resistance determines (together with other things) the Thiele parameter Qt.
When placing another driver in series You add that driver's DC-resistance (e.g. 5 Ohm) to the combined generator resistance. That will spoil any cabinet design which depends on a certain value of Qt. In most cases You will end up with a "boom box".
So don't wire loudspeakers in series if possible.

Ruediger

[toddalin]

There are actually two ways to do this.

You can wire the speakers in series in each cabinet and wire the two cabinets in parallel (as you mentioned), or you can wire the speakers in parallel in each cabinet and wire the two cabinets in series.

In either case, each speaker receives the same load and I don't know that there is a sonic difference one way or the other, but you could try both.

[JBL 4645]

A low frequency speaker "sees" a generator impedance of hopefully much less than an Ohm. It consists of:
a) the amplifier's output impedance, e.g. 0.04 Ohm
b) cable resistance, e.g. 0.1 Ohm
c) resistance of series coil in the crossover, e.g. 0.5 Ohm
When using an active crossover You can get rid of "c", and it pays to invest in "b" (thicker cables).
This combined generator resistance determines (together with other things) the Thiele parameter Qt.
When placing another driver in series You add that driver's DC-resistance (e.g. 5 Ohm) to the combined generator resistance. That will spoil any cabinet design which depends on a certain value of Qt. In most cases You will end up with a "boom box".
So don't wire loudspeakers in series if possible.

Ruediger

Ruediger

I forget about loudspeaker cable resistance!

Is it not best to keep all the cables leading to the loudspeakers at equal length despite one being nearer to the amps (same length)!

So how should you test the impedance with the multi-volt-meter attached to the loudspeaker cable ends and what should you be looking for that is good and bad about the way it’s wired up?

[Ruediger]

I searched for "EV 3512" and found "EV TL3512". Are that Your boxes?

The TL3512 are "bass-reflex" or "vented", You (me ?:) 1st need to check what a proper alignment (box tuning) would be for the speakers. 1st of all tell us what boxes You use.

Then use 2 + 2, 2 speakers on the left channel and 2 speakers on the right channel, wire them parallel to get 4 Ohms. Do NOT bridge the amp, connect one speaker pair to the left channel, and one pair to the right channel.

If You want mono-sub, connect left and right by using a proper Y-cable at the amp's input. 1st tell us how You are driving the amp.

Ruediger

[rlsound]

Those are the boxes.

I'd have to run another line from the amp, since there is only a single run from the amp, to do the 2+2, non-bridged operation.


There is no applied EQ.

Thanks for the confirmation guys.

[Ruediger]

Somehow I thought You were running JBL drivers in those EV boxes. But that seems to be an error of mine. Are You running the EV boxes with the original EV drivers in them?

How are You driving the boxes? What is sitting in front of the amp? An active xover?

Ruediger

[rlsound]

It's the EV DL18 drivers in the boxes. Not a very good driver IMHO. I would like to replace them with the EVX series or JBL 2242, though that will probably never going to happen.

Its a Dolby processor driving the amp, a simple 50/100hz jumper that controls frequency. This processor is known for taking out subwoofers because it uses bass management from the screen speakers but also pumps in the subwoofer track from the digital sound as well.

We are having extra trouble on this screen, as I'm running the gain on the amp at 9 o clock where we are running the gains full up on all the others with out the subs bottoming out. Gains full up wasn't my idea, it started before I started working there.

I thought there was a problem impedance issue with this system, but its probably something up the chain.

Other screen, we have two of this boxes running on a bridged EX4000 and kept blowing them up, I told the tech I thought there was too much power running through them and he didn't think there was....

Says alot.

[Ruediger]

There is a datasheet of the speakers on the net. That tells You the low frequency limits and the power handling capacity.

If Your speakers die from over-excursion then You need to change the electronics setup. Don't ask me, see the manuals :)

If Your speakers die from overheating (burned voice coil) then You can do something:

Mount the speakers "reversed", with the diaphragm facing the inner part of the box and the magnet assembly on the outside. That way cooling is improved.

The box's net volume will become larger by this as the driver does not any longer occupy space in the box. That will spoil Your boxes' alignment unless You compensate.

Check the driver's data sheet for "volume displaced by the driver" or so. Put a piece of styrofoam (as big as the displaced volume) into the box to compensate for the missing volume displacement.

Now that You have reversed the drivers YOU MUST REVERSE THE CABLE'S POLARITY. Connect red to where black was and black to where red was.

Ruediger

[rlsound]

Clever!


I'll have to try that!

[JBL 4645]

There is a datasheet of the speakers on the net. That tells You the low frequency limits and the power handling capacity.

If Your speakers die from over-excursion then You need to change the electronics setup. Don't ask me, see the manuals :)

If Your speakers die from overheating (burned voice coil) then You can do something:

Mount the speakers "reversed", with the diaphragm facing the inner part of the box and the magnet assembly on the outside. That way cooling is improved.

The box's net volume will become larger by this as the driver does not any longer occupy space in the box. That will spoil Your boxes' alignment unless You compensate.

Check the driver's data sheet for "volume displaced by the driver" or so. Put a piece of styrofoam (as big as the displaced volume) into the box to compensate for the missing volume displacement.

Now that You have reversed the drivers YOU MUST REVERSE THE CABLE'S POLARITY. Connect red to where black was and black to where red was.

Ruediger

Kinder like this then!

I’m running some sine wave tests at the moment while Earthquake plays I’m a little sceptical what are the pros and cons of it being this way around? First time I’ve tried it. It was a bit of pig to hold and mount the allenkeys screws fitted in while holding this, heavy sub!

[Allanvh5150]

It will make a difference but only in the fact that the cabinet will have a larger volume. As far as operation is concerned, having the speaker on the inside of the box or on the outside should make no difference as long as the box is calculated correctly.

Allan.

[Ruediger]

It makes a difference when the wavelength of the radiated sound is (roughly) less or equal the size of the obstacles.

You should not do that with a 4430.

But JBL does it with the "Dance3" disco system.

Ruediger

[rlsound]

TAD/JSX also does this with their cinema systems.

[JBL 4645]

It makes a difference when the wavelength of the radiated sound is (roughly) less or equal the size of the obstacles.

You should not do that with a 4430.

But JBL does it with the "Dance3" disco system.

Ruediger

http://www.jblpro.com/pub/cspels/Dance3%205-5-03.pdf